Over the past several decades, the semiconductor integrated circuit (IC) industry has experienced rapid growth. The semiconductor integrated circuit (IC) is basically an assembly of semiconductor electronic components, fabricated as a single unit, in which miniaturized active devices (such as transistors and diodes) and passive devices (for example, capacitors and resistors) and their interconnections are built up on a thin substrate of semiconductor material (such as silicon). The integrated circuits are used in almost any electronic device today. Technological advances in IC design and material have produced generations of ICs where each generation has smaller and more complex circuits than previous generations. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs.
Along with those benefits, such scaling down has also increased the complexity of IC processing and manufacturing. For these advances to be realized, similar developments in IC processing and manufacturing are needed. One area is the interconnects, or contact structures between the transistors and other devices. Although existing methods of fabricating IC devices have been generally adequate for their intended purposes, they have not been entirely satisfactory in all respects.